The great dream of cars running on sustainable petrol has not bitten the dust. Here's why.

Polysaccharide molecules such as cellulose, seen here, are long chains of sugars that are very hard to break apart. Enzymes – proteins that can degrade polysaccharides – have many industrial uses.
CeresVesta/WikipediaApril 24, 2017

Outdoor air pollution causes 3.3 million premature deaths a year, mainly in Asia. And without policies to cut particulate pollution from traffic, industry and home biofuels, the deaths could double by 2050.

An ancient form of energy: a wood pellet manufacturing facility in upstate New York.
thewildcenter/flickrSeptember 16, 2015